The present invention relates generally to multiframe TDM (time division multiplex) communication systems, and more specifically to parity check error detection for multiframe TDM data.
With current TDM digital transmission systems, a parity bit is derived from data bits of each channel of a frame by counting binary 1's such that if there is an odd (or even) number of binary 1's in the channel, the parity bit is a 1, and if there is an even (or odd) number of 1's in that channel, the parity bit is a 0. As many times slots, or parity check fields are reserved in each frame as there are channels in it. The parity bits derived from all channels of the frame are inserted respectively to the parity check fields and transmitted. At a receiving end, a parity bit is derived from the received data bits of each channel and compared with the transmitted parity bit of the corresponding channel to detect an error in that channel is there is a mismatch between them.
However, to meet the increasing volume of information being transmitted with a reduced overhead, it is desirable to perform parity check on a per multiframe basis, rather than on a per frame basis.